Field of the Invention
This invention relates generally to pipe inspection systems employing a camera head connected to the end of a push-cable payed out from a rotatable cable drum.
Description of the Related Art
There are many situations where it is desirable to internally inspect long lengths of pipe that are already in place, either underground, in a building, or underwater. For example, sewer and drain pipes frequently must be internally inspected to diagnose any existing problems and to determine if there are any breaks causing leakage or obstructions impairing the free flow of waste. It is also important to internally inspect steam pipes, heat exchanger pipes, water pipes, gas pipes, electrical conduits, and fiber optic conduits for similar reasons. Frequently, pipes that are to be internally inspected have an internal diameter of six inches or less, and these pipes may make sharp turns. It is sometimes necessary to internally inspect several hundred feet of pipe.
Conventional video pipe inspection systems include a video camera head that is forced down the pipe to display the pipe interior on a video display. The inspection is commonly recorded using a video recorder (VCR) or digital video disk (DVD). Conventional video pipe inspection systems have included a semi-rigid push-cable that provides an electromechanical connection between the camera head that encloses and protects the video camera and a rotatable push reel or cable storage drum that is used to pay out push-cable and force the camera head down the pipe. Examples of suitable video push-cables are disclosed in U.S. Pat. No. 5,457,288 issued Oct. 10, 1995 to Mark S. Olsson and U.S. Pat. No. 5,808,239 issued Sep. 15, 1998 to Mark S. Olsson. The video camera head design and the manner in which it is connected to the push-cable are important to the performance and reliability of a video pipe inspection system.
Conventional pipe inspection systems use a semi-rigid push-cable to move the camera head down a length of pipe. The push-cable must be resilient and have enough flexibility to enable the camera head to negotiate turns. The types of push-cables used in conventional pipe inspection systems limit the turn radius through which the camera may pass, making it extremely difficult, for example, to inspect the interior of a toilet drain or a sink drain due to the tight turns of their piping.
A conventional video pipe inspection system includes a reel or drum for storage of the coils of the push-cable. The reel or drum is typically supported on a frame for rotation about a horizontal or a vertical axis for paying out the push-cable and for rewinding the push-cable for storage. A slip-ring assembly is typically included in the hub and/or axle of the reel or drum to continue electrical connections between the end of the push-cable and external circuits that power the camera head and receive video signals therefrom. Existing systems tend to be heavy and unwieldy in field operations, suffering in portability in order to store hundreds of feet of semi-rigid push-cable around the reel or inside the drum. Traditional storage drums are difficult to remove from the frame of the system, difficult to clean, and can be used only with a single proprietary inspection camera and connection system for which they are designed. Additionally, because of the design of their push-cable and the size of camera heads commonly used, conventional pipe inspection systems cannot negotiate extremely small-bore passages and extremely tight turns.